Cooperative effects of Coulomb and electron-phonon interactions in the two-dimensional 16-band d-p model for iron-based superconductors

We study the electronic states and the superconductivity in the two-dimensional 16-band d-p model coupled with A_1g, B_1g, and E_g local phonons and obtain the rich phase diagram including the magnetic-, charge-, and orbital-ordered phases on the parameter plane of the Coulomb and electron-phonon interactions. When the electron-phonon interaction is dominant, the charge fluctuations induce the s₊₊ -wave superconductivity, while when the Coulomb interaction is dominant, the magnetic fluctuations induce the s_± -wave superconductivity. Remarkably, the orbital fluctuations are enhanced due to the cooperative effects of the Coulomb and electron-phonon interactions and induce the s₊₊ -wave and the nodal s_± -wave superconductivities.